Flame retardant polymer compositions

ABSTRACT

Polymers are flame-retarded by novel combinations of additives comprising: 
     A. a specified compound of iron, cobalt, nickel, tin or antimony, 
     B. an alkali metal chloride, bromide or iodide, and 
     C. an organic acid or inorganic acid salt. Alternatively, additive (c) may be an integral part of the polymer in whole or in part.

This is a division of application Ser. No. 396,632, filed Sept. 12, 1973now U.S. Pat. No. 3,956,139.

This invention is directed to novel combinations of additives which havethe effect of flame-retarding polymers in which they are incorporated.

The use of halogen compounds as flame retardant additives for a broadspectrum of polymers is well known. Significant retardant activity hasbeen limited, however, to those halogen compounds which are volatile,unstable or reactive at polymer combustion temperatures. Organicchlorine and bromine compounds typically fill the retardant requirementand are widely used as polymer flame retardants. The volatility andinstability of these compounds to heat and light, however, have oftenimposed serious limitations on polymer processing conditions and finalproperties.

It is also well known that the retardant activity of organic halogencompounds can be greatly enhanced by the use of certain metallicsynergists, of which antimony oxide is the best known and most widelyused. Such use of synergists, however, frequently accentuates thedeficiencies associated with the use of organic halogen compounds.

Effective use of non-volatile, thermally stable halogen compounds asflame retardants has been limited to a few reactive types, such ashalides of zinc, cadmium and lead, which react advantageously withspecific polymers during combustion. No way has previously been found toobtain a high degree of flame retardant activity with halogen compoundswhich are stable, non-volatile and unreactive toward the polymer. Theseinclude halogen compounds of the widest availability, such as the commonalkali halides. Such compounds normally behave as inert fillers duringpolymer combustion, thereby providing a very low degree of flameretardancy.

EXPOSITION OF THE INVENTION

It has now been found that polymers may be effectively flame retarded bya 3-component additive combination comprising:

A. A COMPOUND OF IRON, COBALT, NICKEL, TIN OR ANTIMONY,

B. AN ALKALI METAL CHLORIDE, BROMIDE OR IODIDE, AND

C. AN ACID WHICH MAY BE AN INTEGRAL PART OF THE POLYMER IN WHOLE OR INPART OR AN INORGANIC ACID SALT.

These combinations are found to be synergistic in their flame-retardingeffect, providing a total effect significantly greater than the sum ofthe contributions of the three components used individually or in pairs.Thus, while alkali halides provide only minor flame retarding effectswhen used alone or in combination with (a) or (c), they provide majoreffects in combination with both (a) and (c). Further, (a) and (c), usedindividually or in combination, produce relatively minor effects in theabsence of the halide.

It is a further advantage of this invention that all three componentsmay be selected from materials which are substantially non-volatile(i.e., they are not subject to significant loss (loss to an extent whichwould impair their effectiveness) by volatilization during or afterprocessing of the polymer), substantially stable to atmospheric moistureand stable at conventional polymer processing temperatures. In addition,the practice of this invention permits the effective flame-retardant useof halogen compounds which are non-toxic.

Polymers which may be flame retarded in accordance with this inventionare hydrocarbon polymers, nitrile-containing polymers,carboxylic-containing polymers and carboxylate ester-containingpolymers. Typical examples of these polymers include polyolefinplastics, such as polyethylene, polypropylene and similar plasticpolymers or copolymers of α-olefins of the ethylene series, polystyrene,polyisobutylene, elastomers based on conjugated dienes, includinghomopolymers of butadiene (emulsion-prepared or solution-prepared),isoprene (natural rubber or synthetic cis-polyisoprene) and copolymersof such dienes with copolymerizable ethylenically unsaturated monomerssuch as styrene, e.g., SBR (solution-prepared or emulsion-prepared),ethylene-propylene copolymer rubbers andethylene-propylene-non-conjugated diene (e.g., dicyclopentadiene,1,4-hexadiene, methylene norbornene) terpolymer rubbers, poly-4-methylpentene-1 and polymers of other substituted butenes, pentenes, hexenes,etc.; copolymers of hydrocarbon dienes with copolymerizableethylenically unsaturated monomers such as acrylonitrile, e.g., NBR,styrene-acrylonitrile resins, ABS plastics (whether mixtures ofstyrene-acrylonitrile resin with butadiene-acrylonitrile rubber or witha graft copolymer of styrene and acrylonitrile on polybutadiene orbutadiene-styrene copolymer); polymers and copolymers of acids such asmaleic acid, fumaric acid, acrylic acid, methacrylic acid and itaconicacid; polymethacrylates and polyacrylates.

Compound (a) is selected from the oxides, sulfates, carbonates,acetylacetonates and carboxylates of iron, cobalt, nickel, tin andantimony, or the bis-cyclopentadienyl compounds of iron, cobalt andnickel, although the oxides, sulfates and acetylacetonates are thepreferred metallic compounds for use in this invention. The carboxylatesare the salts of saturated or unsaturated mono- or poly-carboxylic acidsof aliphatic, alicyclic, aromatic, heterocyclic, polycyclic, or mixedtypes having up to 20 carbon atoms. Substituents may also be presentprovided that they do not interfere with the fire-retardant activity ofthe combination of (a), (b) and (c). Such substituents preferably do notinclude halogen, in order that the aforementioned deficiencies oforganic halogen compounds may be avoided. Carboxylates relatively highin metal content are preferred. Examples of suitable carboxylatesinclude acetate, oxalate, tartrate and citrate. The preparation andproperties of the bis-cyclopentadienyl compounds are reported inKirk-Othmer, Encyclopedia of Chemical Technology, 2nd Ed., Vol. 6, pp.696-698, and in the review articles cited therein, all of which areincorporated by reference herein.

Both anhydrous and hydrous forms of compound (a) are operable. Likewise,normal, basic and acidic forms, e.g., basic ferric acetate, acidoxalates and the like, may be employed. The degree and amount of suchacidity or basicity must, however, be taken into account in determiningthe requisite amount of compound (c), described below, to be used.

The metallic compound is used in amounts which are approximately 5 to100% by weight of the amount which is chemically equivalent to thehalogen atoms present. For example, the amount of ferric oxidechemically equivalent to the halogen atoms present in a compositioncontaining 0.075 gram-formula weight of an alkali halide would be##EQU1## where 2 is the number of iron atoms in each Fe₂ O₃ formula, 3is the valency of each iron atom and 159.7 is the formula weight of Fe₂O₃. Amounts appreciably in excess of chemical equivalency contributelittle to the flame retardancy. Preferably, an amount ranging from 25%to 75% of the equivalent amount is employed. Mixtures or mixed salts ofthe metallic compounds may also be employed.

Halide (b) is an alkali metal chloride, bromide or iodide. The amount ofhalide employed in the practice of this invention is not critical butwill depend on the balance desired between degree of flame retardationand other properties. Flame retardation will normally increase as largeramounts of halide are employed, while other properties likewise departfurther from those of the unretarded composition. While a loading of0.075 gram-mole of halide per hundred grams of polymer has been foundsuitable, greater or lesser amounts may be employed without departingfrom the spirit of this invention. Normally, a minimum of about 0.003gram-mole of halide per hundred grams of polymer will be required forsignificant flame retardancy. For a given degree of flame retardancy,the amount required will depend on the choice of specific components.Mixtures of halides may also be used.

Component (c) is an organic acid, or an inorganic acid salt, having anacid ionization constant in excess of 10⁻ ⁶ and which is substantiallynon-volatile at conventional polymer processing temperatures. As statedabove, an acid which is substantially non-volatile is not subject tosignificant loss (loss to an extent which would impair itseffectiveness) by volatilization during or after processing of thepolymer. In general, acids containing relatively high concentrations ofacid moieties within the molecule, and having melting points below theirvaporization and decomposition temperatures, are more effective and arepreferred. Examples of suitable organic acids are acids such assuccinic, glutaric, adipic, pimelic, suberic, tartaric, m-phthalic andcitric acids, mono- and dialkyl phosphonic and phosphoric acids, such asmethylphosphonic acid and diethyl phosphate, and sulfonic acids.Examples of operable inorganic acid salts are bisulfates such aspotassium bisulfate.

The amount of component (c) should range from about 25% to 325% byweight, based on chemical equivalency to the sum of the amounts ofcompound (a) and halide (b). The amount of component (c) is adjusted inthe case (i) in which the organic polymer is a carboxylic-containingpolymer so that the carboxylic content of such polymer together with theamount of component (c) provide the stated chemical equivalency. In thissituation, component (c) is omitted when the equivalency requirement ismet by the polymer alone. The amount of component (c) is based only onequivalency with the amount of halide (b) in the case (ii) in whichcompound (a) is a salt of an acid having the same ionization constant asor a higher ionization constant than that of component (c). Thepreferred amounts of component (c) are between 75% and 200% by weight ofthe indicated chemical equivalency. Larger amounts than 325% by weightof such equivalency contribute little or nothing additional to flameretardancy and are generally deleterious to other properties. Smalleramounts than 25% by weight of such equivalency contribute little toflame retardancy. Mixtures of acids may also be employed.

In order to illustrate the method of determining the indicated chemicalequivalency, the amount of succinic acid chemically equivalent to thesum of compounds (a) and (b) in a composition containing 0.075gram-formula weight of an alkali halide and one gram of ferric oxidewould be ##EQU2## where 2, 3 and 159.7 in the first fraction are,respectively, the number of iron atoms in each Fe₂ O₃ formula, thevalency of each iron atom, and the formula weight of Fe₂ O₃, and 118.1and 2 in the second fraction are, respectively, the molecular weight ofsuccinic acid and the number of acidic moieties having an ionizationconstant greater than 10⁻ ⁶ in each succinic acid molecule. As anexample of case (ii), the amount of citric acid monohydrate which ischemically equivalent to the halide alone in a composition containing13.1 gr. potassium iodide and 3.7 gr. ferrous sulfate (HSO₄ ⁻ being astronger acid than the strongest acid group in citric acid) would be##EQU3## where 166.0 is the formula weight of potassium iodide, and210.1 and 3 are, respectively, the molecular weight of the acid and thenumber of acid moieties having an ionization constant greater than10.sup.⁻⁶ in each acid molecule.

The flame retardant components are incorporated into the polymer byconventional polymer compounding techniques. The order to mxing is notcritical to the performance of the invention, but it is generallypreferred that compound (a) be incorporated with, or prior to, halide(b) and/or component (c). If desired, the components may be incorporatedinto the polymer in amounts larger than those desired for the finalcomposition and the resulting masterbatch is combined subsequently withadditional polymer.

It is also clear that any amount of polymer smaller than that desiredfor the final composition may be combined with the components bysuitable techniques, the resulting fire-retardant concentrate (ormasterbatch) being combined subsequently with additional polymer in theconventional manner. Such a procedure can be useful in facilitatingdispersion of the fire-retardant components in the final composition.Typically, the amount of polymer in the concentrate will rangeapproximately from 10 to 75% of the total weight of concentrate. Withreference to the concentrate, it is of course also possible tosubstitute for the polymer, in whole or in part, such other polymers aswill be suitable to the processing and properties of the finalcomposition and will not prevent operation of the fire-retardant system.Other processing aids and/or other indredients which meet the samerequirements may be included in the concentrate in addition.

The operation of this invention in the flame retardation of ABS polymeris illustrated in the examples below. Compounding of the ABS,polystyrene, acrylic resin and polypropylene test specimens was carriedout in a conventional manner on a rubber/plastics mill. Slab specimenswere compression molded, and were cut to size and finished as specifiedin ASTM D-2863. The ABS polymer was a gum plastic containing 22%acrylonitrile, 23% butadiene and 55% styrene.

Testing of specimens was carried out by ASTM Method D-2863,"Flammability of Plastics Using the Oxygen Index Method". Oxygen Indexis the minimum concentration of oxygen, expressed as percent by volume,in a slowly rising mixture of nitrogen and oxygen, that will justsupport the combustion of a material burning under equilibriumconditions of candle-like burning. Thus, higher Oxygen Index indicatesdecreased relative flammability. Since the method provides a continuousnumerical scale for the assignment of relative flammability ratings, itis especially appropriate for illustrating differences in the degree offlame retardation provided by additives and additive combinations.Specimens of the ABS polymer itself have an Oxygen Index of 18.5. "ΔOI"values shown in the examples represent the increases in Oxygen Indexobtained with the specified additive-containing composition relative tothe Index of the ABS and other polymers. Parts of additives shown areparts by weight per hundred parts of polymer. Moles are parts divided byformula weight.

EXAMPLE 1

The following demonstrates the operability of alkali halides, when usedin combination with acidic and metallic components, in reducing theflammability (increasing the Oxygen Index) of ABS polymer. Powderedmixtures of the components, incorporated in ABS in the amountsindicated, gave the ΔOI's shown:

    __________________________________________________________________________    Halide      Parts                                                                              Moles                                                                             Acid Parts                                                                             Moles                                                                             Metal Cpd.                                                                            Parts                                                                             Moles                                                                             ΔOI                   __________________________________________________________________________    (a) Potassium Iodide                                                                      12.5 .075                                                                              succinic                                                                           13.3                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +4.9                        (b) Sodium Bromide                                                                        7.8  .075                                                                              succinic                                                                           13.3                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +2.9                        (c) Sodium Chloride                                                                       4.4  .075                                                                              succinic                                                                           13.3                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +1.9                        __________________________________________________________________________

In contrast to ABS polymer, which after ignition burned continuously atoxygen concentrations of 18.5% and higher, compositions (a), (b) and (c)were self-extinguishing at oxygen concentrations below 23.4, 21.4 and20.4%, respectively.

When powdered mixtures with one component omitted, as indicated, wereincorporated in ABS, the following results were obtained:

    __________________________________________________________________________    Halide      Parts                                                                              Moles                                                                              Acid                                                                              Parts                                                                             Moles                                                                             Metal Cpd.                                                                            Parts                                                                             Moles                                                                             ΔOI                   __________________________________________________________________________    (d) Potassium Iodide                                                                      12.5 .075                                                                              succinic                                                                           13.3                                                                              .113                                                                              None    --  --  +0.6                        (e) Potassium Iodide                                                                      12.5 .075                                                                              None --  --  Ferric Oxide                                                                          1   .006                                                                              +1.3                        (f) None    --   --  succinic                                                                           13.3                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +0.7                        __________________________________________________________________________

Additional ABS control compositions with the following ingredients gavethe results shown:

    __________________________________________________________________________    Halide      Parts                                                                              Moles                                                                              Acid                                                                              Parts                                                                             Moles                                                                             Metal Cpd.                                                                            Parts                                                                             Moles                                                                             ΔOI                   __________________________________________________________________________    (g) Sodium Chloride                                                                       5    .086                                                                              None --  --  None    --  --  +0.1                        (h) None    --   --  succinic                                                                           10.1                                                                              .086                                                                              None    --  --  +0.2                        (i) None    --   --  None --  --  Ferric Oxide                                                                          1   .006                                                                              +1.1                        (j) Sodium Chloride                                                                       5    .086                                                                              succinic                                                                           10.1                                                                              .086                                                                              None    --  --  +0.1                        __________________________________________________________________________

The ΔOI comparisons: (a) > (d) + (i), (a) > (e) + (h), (c) > (f) + (g),(c) > (i) + (j) and (c) > (g) + (h) + (i) illustrate the synergism ofthe 3-component combinations, which provide ΔOI's in excess of the sumof the contributions of the components used in the same or similaramounts in other combinations.

Examples 2, 3 and 4 illustrate the operability of a variety of organicacids or inorganic acid salts as the acid component.

EXAMPLE 2

Successive addition of powdered components, in the order indicated, toABS polymer, gave the results shown:

    __________________________________________________________________________      Metal Cpd.                                                                            Parts                                                                             Moles                                                                             Halide    Parts                                                                             Moles                                                                             Acid  Parts                                                                             Moles                                                                             ΔOI                   __________________________________________________________________________    (k) Ferric Oxide                                                                        1   .006                                                                              Potassium Iodide                                                                        12.5                                                                              .075                                                                              Potassium                                                                           15.3                                                                              112 +3.1                                                            Bisulfate                                 (l) Ferric Oxide                                                                        1   .006                                                                              Potassium Iodide                                                                        12.5                                                                              .075                                                                              m-phthalic                                                                          18.7                                                                              .113                                                                              +2.1                          Compositions with one or more components omitted gave                       the following results:                                                          Halide    Parts                                                                             Moles                                                                             Acid         Parts                                                                              Moles                                                                              Metal Cpd.                                                                           ΔOI                   __________________________________________________________________________    (m) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Potassium Bisulfate                                                                        15.3 .112 None   +1.2                        (n) None    --  --  Potassium Bisulfate                                                                        11.6 .085 None   +0.8                        __________________________________________________________________________

Again, ΔOI comparison shows (k) > (m) + (i).

EXAMPLE 3

Addition of powdered ferric oxide and potassium iodide mixtures to ABScontaining the admixed acid shown, gave the results indicated:

    __________________________________________________________________________    Halide      Parts                                                                             Moles                                                                              Acid                                                                              Parts                                                                             Moles                                                                             Metal Cpd.                                                                            Parts                                                                             Moles                                                                             ΔOI                    __________________________________________________________________________    (o) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Tartaric                                                                           16.9                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +5.7                         (p) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric*                                                                            23.7                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +5.8                         __________________________________________________________________________     *Monohydrate used throughout.                                            

EXAMPLE 4

Incorporation of a powdered mixture of the components shown into ABSgave the result indicated:

    __________________________________________________________________________    Halide      Parts                                                                             Moles                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Cpd.                                                                            Parts                                                                             Moles                                                                             ΔOI                     __________________________________________________________________________    (q) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Adipic                                                                            16.5                                                                              .113                                                                              Ferric Oxide                                                                          1   .006                                                                              +2.6                          __________________________________________________________________________

EXAMPLE 5

This example illustrates that a variety of metallic compounds areoperable in combination with acids and halides.

ABS compositions containing the 3 components shown gave the followingtest results:

    __________________________________________________________________________    Halide      Parts                                                                             Moles                                                                              Acid Parts                                                                             Moles                                                                              Metal Compound                                                                          Parts                                                                             Moles                                                                             ΔOI                __________________________________________________________________________    (r) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric                                                                              23.7                                                                              .113                                                                              Tris(2,4-pentane-                                                                        4.7 .013                                                                              +8.3                                                       diono)iron                                  (s) Sodium Chloride                                                                        4.4                                                                              .075                                                                              Citric                                                                              23.7                                                                              .113                                                                              Tris(2,4-pentane-                                                                        4.7 .013                                                                              +5.3                                                       diono)iron                                  (t) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Succinic                                                                            13.3                                                                              .113                                                                              Tris(2,4-pentane-                                                                        4.7 .013                                                                              +4.4                                                       diono)iron                                  (u) Potassium Iodide                                                                      13.1                                                                              .079                                                                              Citric                                                                              15.3                                                                              .073                                                                              Ferrous Sulfate                                                                          3.7 .013                                                                              +4.9                                                       (crystal)                                   (v) Potassium Iodide                                                                      13.1                                                                              .079                                                                              Potassium                                                                           10.8                                                                              .079                                                                              Ferrous Sulfate                                                                          3.7 .013                                                                              +1.9                                         Bisulfate     (crystal)                                   (w) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Succinic                                                                            13.3                                                                              .113                                                                              Stannous Oxide                                                                           2.5 .019                                                                              +1.9                     (x) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Succinic                                                                            13.3                                                                              .113                                                                              Antimony Trioxide                                                                        1.8 .006                                                                              +1.5                     (y) Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric                                                                              21.6                                                                              .103                                                                              Bis(2,4-pentane-                                                                         5.5 .019                                                                              +5.7                                                       diono)nickel                                                                  dihydrate                                   (y') Potassium Iodide                                                                     12.5                                                                              .075                                                                              Citric                                                                              23.7                                                                              .113                                                                              Cobalt Oxide                                                                             1.0 .006                                                                              +2.0                                                       (Co.sub.2 O.sub.3)                          __________________________________________________________________________     Note:                                                                         The pentanediono compounds are acetylacetonates.                         

Compositions with one or more components omitted gave the followingresults:

    __________________________________________________________________________    Halide                                                                              Acid                                                                              Parts                                                                             Moles                                                                              Metal Compound                                                                              Parts                                                                              Moles                                                                             ΔOI                           __________________________________________________________________________    (z) None                                                                            Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pentanediono)iron                                                                   4.7  .013                                                                              +3.0                                (a') None                                                                           None                                                                              --  --  Antimony Trioxide                                                                            10   .034                                                                              +0.9                                __________________________________________________________________________     Note:                                                                         The formula Sb.sub.2 O.sub.3 was used as the basis for calculating moles      of antimony trioxide in the above.                                       

ΔOI comparison again shows: (s) > (g) + (z).

Comparison of (x) and (d) illustrates that less than 2 parts of antimonytrioxide, when used in combination with acid and halide, makes acontribution (0.9) equivalent to that of 10 parts of the trioxide whenused alone (a').

EXAMPLE 6

This example illustrates the use of Styron 666U (a general purposepolystyrene having an Izod Impact Strength of 0.2 ft.lb./in. of Notch at73° F. and a Vicat Softening Point of 212° F.) as a suitable polymer inwhich the fire retardant systems of the present invention can be used.

    __________________________________________________________________________    Halide       Parts                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Compound                                                                           Parts                                                                             Moles                                                                             OI  ΔOI                 __________________________________________________________________________    (b') None    --  None                                                                              --  --  None       --  --  18.3                                                                              --                        (c') Potassium Iodide                                                                      12.5                                                                              Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pentane-                                                                        4.7 .013                                                                              19.6                                                                              +1.3                                                   diono)iron                                       __________________________________________________________________________

EXAMPLE 7

This example illustrates the use of Lucite 130 (an acrylic resin havingan Izod Impact Strength of 0.3 at 73° F., a specific gravity of 1.18,and a deflection temperature (264 psi) of 166° F.) as a suitable polymerin which the fire retardant systems of the present invention can beused.

    __________________________________________________________________________    Halide       Parts                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Compound                                                                           Parts                                                                             Moles                                                                             OI  ΔOI                 __________________________________________________________________________    (d') None    --  None                                                                              --  --  None       --  --  17.7                                                                              --                        (e') Potassium Iodide                                                                      12.5                                                                              Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pentane-                                                                        4.7 .013                                                                              20.5                                                                              +2.8                                                   diono)iron                                       __________________________________________________________________________

EXAMPLE 8

This example illustrates the use of SBR 1500 (a cold-polymerized,non-pigmented, rosin-acid emulsified, salt-acid coagulated, stainingstyrene-butadiene rubber of 23.5% target bound styrene) as a suitablepolymer in which the fire retardant systems of the present invention canbe used:

    __________________________________________________________________________    Halide       Parts                                                                             Moles                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Compound                                                                         Parts                                                                             Moles                                                                             OI  ΔOI               __________________________________________________________________________    (f') None    --  --  None                                                                              --  --  None     --  --  18.6                                                                              --                      (g') Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pent-                                                                         4.7 .013                                                                              20.0                                                                              +1.4                                                     anediono)iron                                __________________________________________________________________________

All compositions in Examples 8, 9 and 11 were cured with the followingsystem:

    ______________________________________                                        Kadox 15 (zinc oxide) 5 parts                                                 Stearic Acid          1 part                                                  MBT (Mercaptobenzothiazole)                                                                         2.5 parts                                               Sulfur                2 parts                                                 ______________________________________                                    

Slab specimens were compression molded for two hours at 330° F.Specimens were cut to size for testing.

Compounding of rubbers was carried out conventionally on a rubber millwith cool rolls. Molded specimens were cooled prior to removal frompress.

EXAMPLE 9

This example illustrates the use of Paracril BLT(butadiene-acrylonitrile copolymer rubber of medium nitrile content;specific gravity of 0.99; Mooney viscosity (ML-2 at 212° F.) of 80-90)as a suitable polymer in which the fire retardant systems of the presentinvention can be used:

    __________________________________________________________________________    Halide       Parts                                                                             Moles                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Compound                                                                         Parts                                                                             Moles                                                                             OI  ΔOI               __________________________________________________________________________    (h') None    --  --  None                                                                              --  --  None     --  --  19.1                                                                              --                      (i') Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pent-                                                                         4.7 .013                                                                              22.5                                                                              +3.4                                                     anediono)iron                                __________________________________________________________________________

EXAMPLE 10

This example illustrates the use of Profax 6523 (propylene homopolymerhaving a Rockwell Hardness (R) of 102 and a Deflection Temperature (264psi) of 58° C.) as a suitable polymer in which the fire retardantsystems of the present invention can be used:

    __________________________________________________________________________    Halide       Parts                                                                             Moles                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Compound                                                                         Parts                                                                             Moles                                                                             OI  ΔOI               __________________________________________________________________________    (j') None    --  --  None                                                                              --  --  None     --  --  17.2                                                                              --                      (k') Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pent-                                                                         4.7 .013                                                                              18.3                                                                              +1.1                                                     anediono)iron                                __________________________________________________________________________

EXAMPLE 11

This example illustrates the use of Royalene 501 (a low gravity,fast-curing, light-colored, non-stainingethylene/propylene/non-conjugated diene rubber polymer) as a suitablepolymer in which the fire retardant systems of the present invention canbe used:

    __________________________________________________________________________    Halide       Parts                                                                             Moles                                                                             Acid                                                                              Parts                                                                             Moles                                                                             Metal Compound                                                                         Parts                                                                             Moles                                                                             OI  ΔOI               __________________________________________________________________________    (l') None    --  --  None                                                                              --  --  None     --  --  18.2                                                                              --                      (m') Potassium Iodide                                                                      12.5                                                                              .075                                                                              Citric                                                                            23.7                                                                              .113                                                                              Tris(2,4-pent-                                                                         4.7 .013                                                                              20.1                                                                              +1.9                                                     anediono)iron                                __________________________________________________________________________

The m' sample sponged upon mold release, slowly returning to correctgauge for testing. While the overall formulation used is non-commercial,the example does illustrate that the flame retardant system of thisinvention is operative in EPDM rubbers.

COMPARATIVE RESULTS WITH RECOGNIZED FLAME-RETARDANT ADDITIVES:

The following are some comparative results obtained in ABS polymer withtypical commercial flame retardant additives:

    ______________________________________                                                               Moles                                                  Additive (pph)         Halogen  ΔOI                                     ______________________________________                                        Poly (vinyl chloride)* (5)                                                                           .079     +2.3                                          Cloran** (5)           .071     +1.0                                          Cloran (5) + Antimony Trioxide (5)                                                                   .071     +2.8                                          Cloran (5) + Antimony Trioxide (11)                                                                  .071     +3.9                                          ______________________________________                                         *stabilized with an organotin additive                                        ** trademark denoting product of UOP Chemical Company                    

Comparison with Example 5 shows that, at equimolar halogen contents, thecombinations of the present invention compare quite favorably in flameretardant effectiveness with additives of the organic halogen type usedeither alone or in combination with antimony trioxide.

Having thus described my invention what I claim and desire to protect byLetters Patent is:
 1. A composition comprising an organic polymerselected from the group consisting of hydrocarbon polymers,nitrile-containing polymers, carboxylic-containing polymers andcarboxylate ester-containing polymers and an effective flame retardantamount of: (a) a compound selected from the group consisting of theoxides, sulfates, carbonates, acetylacetonates, and carboxylates ofiron, cobalt, nickel, tin and antimony and the bis-cyclopentadienylcompounds of iron, cobalt and nickel, said carboxylates being the saltsof an acid selected from the group consisting of acetic, oxalic,tartaric and citric acids; and (b) an alkali metal halide selected fromthe group consisting of chlorides, bromides and iodides; and (c) fromabout 25% by weight to about 325% by weight, based on chemicalequivalency to the sum of the amounts of compound (a) and halide (b), ofa compound selected from the group consisting of succinic, glutaric,adipic, pimelic, suberic, tartaric, m-phthalic and citric acids, mono-and dialkyl phosphonic and phosphoric acids, organic sulfonic acidshaving an acid ionization constant in excess of 10.sup.⁻⁶ and which issubstantially non-volatile at conventional polymer processingtemperatures, and potassium bisulfate, except that the amount ofcomponent (c) is based only on equivalency with the amount of halide (b)in the case in which compound (a) is a salt of an acid having the sameionization constant as or a higher ionization constant than that ofcomponent (c); compound (a) being present in an amount which is about 5to about 100% by weight of the amount chemically equivalent to thehalogen atoms present.
 2. The composition of claim 1 in which saidorganic polymer is an ABS plastic.
 3. The composition of claim 1 inwhich said organic polymer is polystyrene.
 4. The composition of claim 1in which said organic polymer is an acrylic resin.
 5. The composition ofclaim 1 in which said organic polymer is a styrene-butadiene copolymer.6. The composition of claim 1 in which said organic polymer is anacrylonitrile/butadiene copolymer.
 7. A masterbatch comprising fromabout 10 to about 75%, based on the total weight of the masterbatch, ofan organic polymer selected from the group consisting of hydrocarbonpolymers, nitrile-containing polymers, carboxylic-containing polymersand carboxylate ester-containing polymers and from about 90 to about25%, based on the total weight of the masterbatch, of a flame retardantcomposition comprising: (a) a compound selected from the groupconsisting of the oxides, sulfates, carbonates, acetylacetonates, andcarboxylates of iron, cobalt, nickel, tin and antimony and thebis-cyclopentadienyl compounds of iron, cobalt and nickel, saidcarboxylates being the salts of an acid selected from the groupconsisting of acetic, oxalic, tartaric and citric acids; and (b) analkali metal halide selected from the group consisting of chlorides,bromides and iodides; and (c) from about 25% by weight to about 325% byweight, based on chemical equivalency to the sum of the amounts ofcompound (a) and halide (b), of a compound selected from the groupconsisting of succinic, glutaric, adipic, pimelic, suberic, tartaric,m-phthalic and citric acids, mono- and dialkyl phosphonic and phosphoricacids, organic sulfonic acids having an acid ionization constant inexcess of 10⁻ ⁶ and which is substantially non-volatile at conventionalpolymer processing temperatures, and potassium bisulfate, except thatthe amount of component (c) is based only on equivalency with the amountof halide (b) in the case in which compound (a) is a salt of an acidhaving the same ionization constant as or a higher ionization constantthan that of component (c); compound (a) being present in an amountwhich is about 5 to about 100% by weight of the amount chemicallyequivalent to the halogen atoms present.